David Cameron has defended the decision of the Conservative party to suspend Nadine Dorries for leaving Westminster to appear on a reality show, insisting it was the "right thing to do".

The prime minister made his comments as it emerged that the Westminster watchdogis considering whether to investigate a complaint it received over her decision to take part in I'm a Celebrity … Get Me Out of Here.

Dorries's forthcoming appearance on the jungle-based reality show, which starts on Sunday and is set to earn the MP for Mid Bedfordshire £40,000, could take her away from her constituency and parliamentary duties for up to a month.

Speaking on ITV's This Morning, the prime minister, who came back from a trip to the Middle East on Wednesday afternoon, confirmed that he, like other colleagues, had not been informed that Dorries was planning to appear on I'm a Celebrity. He said the chief whip, Sir George Young, had taken the "very sensible decision" to ensure she is "no longer a Conservative MP".

"The chief whip took the view – and I back this completely – that she had made the decision to go out and do this programme and that meant she couldn't be in parliament, she couldn't represent her constituents and I think people do expect MPs to be doing either one or two of those things, particularly when parliament is sitting."

Dorries has insisted that Cameron, with whom she has repeatedly clashed, would be glad to see the back of her. "I am a thorn in his side," she said. "He will be relieved."

But Cameron said he wanted Conservative MPs doing their job.

"Obviously Nadine and I have had a few run-ins over the years but I think the chief whip has done the right thing."

While fellow elected MPs prepared for a normal working day on Thursday, a topless Dorries was photographed sunbathing in Queensland as she relaxed before the programme goes on air this weekend.

The show, which will run daily, typically involves gruelling challenges, including "bushtucker trial" meals which have in the past featured bugs, crocodile penis and kangaroo testicles.

The parliamentary commissioner for standards, John Lyon, will examine a complaint received about whether she may have breached the code of conduct for MPs by being absent from the Commons.

A spokeswoman for the commissioner confirmed a complaint had been lodged on Wednesday. "The complaint is being considered in the usual way. We usually respond within five working days," she said.

The health secretary told ITV1's Daybreak: "A lot of people are very worried about it. And I think we want MPs where they should be, voting in the House of Commons."

When Dorries returns to the UK, she will be summoned to meet Young to discuss whether she will have the party whip restored.

Dorries remains blissfully cut off from the furore as she and other participants, who include the EastEnders actor Charlie Brooks and former world darts champion Eric Bristow, are in "lockdown" before the show, meaning they are barred from any communication with the outside world.

Dr Sarah Wollaston, the Conservative MP for Totnes, has said Dorries, who is paid an annual Commons salary of £65,738, should resign her seat if she wants to be a celebrity and should hand her appearance fee to the taxpayer. Michael Fabricant, the Tory MP for Lichfield, said Dorries had "let down her colleagues and her constituency".

But Dorries claimed in the press material for the show that her appearance was the perfect opportunity to prove that politicians were "normal".

"A lot of people don't vote and if they can see I am a normal mother who comes from a poor background and who didn't go to a posh school, they may think they can be a politician too. Maybe they will trust us more," she said.

Dorries listed the "special occasions" she would miss while in the jungle as "local elections, a byelection, whether President Obama will still be in office or not, and the Tatler ball".